Simplified hydraulic load cell construction

ABSTRACT

A hydraulic load cell of simplified construction has an upper lateral support structure for the piston which eliminates the need for clamping rings and bolts. The support structure comprises an upper bridge ring disposed between the cylinder and piston members and held by integral flanges on said members. The upper bridge ring, and the lower bridge ring where used, may each be provided with arcuate edges to improve cell accuracy. The cell may also be provided with a supplementary shield against contamination and a simplified loading head structure.

United States Patent Chester D. Bradley Darien, Conn.

July 30, 1970 Jan. 1 l, 1972 The A. H. Emery Company New Canaan, Conn.

Inventor Appl. N 0. Filed Patented Assignee SIMPLIFIED HYDRAULIC LOADCELL CONSTRUCTION 14 Claims, 4 Drawing Figs.

U.S. CI 177/208 Int. Cl G01g 5/04 Field of Search... 177/208, 254;73/14] A References Cited UNITED STATES PATENTS 7/1951 Tate l77/208X2,960,328 1 H1960 Tate 177/208 UX 3,145,795 8/1964 Tate 177/2083,177,958 4/1965 Link 177/208 3,261,417 7/1966 Golding 177/208 PrimaryExaminer-Richard B. Wilkinson Assistant Examiner-George H. Miller, Jr.Attorney-Blair, St. Onge and Mayers ABSTRACT: A hydraulic load cell ofsimplified construction has an upper lateral support structure for thepiston which eliminates the need for clamping rings and bolts. Thesupport structure comprises an upper bridge ring disposed between thecylinder and piston members and held by integral flanges on saidmembers. The upper bridge ring, and the lower bridge ring where used,may each be provided with arcuate edges to improve cell accuracy. Thecell may also be provided with a supplementary shield againstcontamination 'and a simplified loading head structure.

BACKGROUND OF THE INVENTION Hydraulic load cells are now widely used forthe weighing of large loads, and they are particularly advantageous forloads which do not lend themselves to weighing by more conventional beamscale-type weighing apparatus. For a general discussion of the structureand theory of operation of a modern hydraulic load cell see US. Pat. No.2,960,328.

In a load cell of the general type described in the abovecited patent,the piston should move freely in an axial direction in the cylinder inresponse to loading if accuracy is to be maintained. To do this thepiston should be supported within the cylinder in such a manner as tooffset side thrusts or the effects of offcenter loading. These mightotherwise cause the piston to bind against the cylinder wall. Thesupport structure, however, should itself be substantially free fromfriction or binding so as not to impair accuracy. In prior cells suchsupport has been provided by an annular stayplate, or in one case astacked pair of annular bridge rings, interposed and clamped in positionbetween the piston and cylinder walls at the upper end of the load cell,and by a single annular bridge ring similarly interposed but not clampedat the lower end of the cell resting over the diaphragm. While thesestructures have been generally satisfactory, constant efforts have beenmade over the years toward improvement.

The use of a clamped support structure at the upper end of the load cellhas been an area of particular concern. Such a structure has typicallyrequired the use of a pair of clamping rings or the like, one beingsecured by bolts to the cylinder and the other similarly secured to thepiston. The clamping rings have served to respectively clamp the innerand outer edges of the stayplate or upper bridge ring pair to the pistonand cylinder members. Naturally, the necessity for separately machinedclamping rings, numerous clamping bolts, plus the time and effortnecessary to accurately position, tap and thread the holes required toreceive the clamping bolts, has added significantly to the complexityand thus to the costs of manufacture and assembly of these prior artcells.

Accordingly, representative objects of the present invention are toprovide an improved hydraulic load cell having a greatly simplifiedlateral support structure for the piston, and other improvements,yielding a less complex cell which is easier to manufacture andassemble, inexpensive, and having increased accuracy and reliability.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

SUMMARY OF THE INVENTION The present invention relates to an improvedhydraulic load cell of simplified construction, and more particularly toa load cell having an improved and simplified support structure for thepiston utilizing an upper bridge ring in place of the prior art clampedstayplate, and other improvements.

the cell of the invention comprises a cylinder member in which a pistonmember is telescopically mounted for reciprocal axial movement. Alateral support structure is provided to keep the piston centered in thecylinder and prevent binding during its axial movement. Typically, thesupport structure comprises a lower bridge ring interposed between thepiston and cylinder members and resting over the cell diaphragm. Thelower bridge ring serves primarily to center the lower end of the pistonand to support the diaphragm over the span between piston and cylinder.In some cells contemplated by the invention, however, the function ofthe lower bridge ring may be performed by other means. Accordingly, theupper bridge ring support structure described hereinafter is notstrictly limited to use in cells employing a lower bridge ring.

The upper bridgering serves to support the upper end of the piston; itis interposed between the piston and cylinder members and is supportedby shoulders which. are preferably in-, tegrally formed on the upper endof the piston and cylinder walls. No additional support beyond theshoulders is necessary; for the upper bridge ring thus eliminating theneed for bolts and the additional machining.

separate clamping rings, required in prior art cells. t

The upper bridge ring is also preferably provided with rounded orarcuate inner and outer diameter edges. The use of arcuate edgeseliminates sharp comers and thus allows the upper bridge ring edges tofreely pivot in rolling manner against the contacting piston andcylinder wall when the bridge ring deflects in response to axialmovement of the piston. Accordingly the chances of binding occurringbetween the upper bridge ring and either the piston or cylinder wallsare minimized, and cell accuracy is improved.

The load cell may also be provided with a supplementary shield over theupper bridge ring to protect against contamination should the mainprotective boot of the load cell fail.

Prior art cells have previously employed arcuated inner and outerdiameter edged on the lower bridge ring to improve accuracy. Preferably,the cell of the invention also uses such a lower bridge ring structure,in combination with the improved upper bridge ring previously described,to obtain optimum load cell performance.

The load cell may still further be provided with a loading assemblycontaining a rolling ball to accommodate offcenter loading or crossloads on the loading head. The loading assembly, however, issimplified'in relation to those in some prior art cells in that the loadblocks employed are freely supported. This eliminates the need forseparate fastening bolts and the machining of holes to receive them.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of thenature and objects of the invention, reference should be had to thefollowing detailed description taken in connection with the accompanyingdrawing, in which: i

Fig. 1 is a front elevation view in section of the improved hydraulicload cell of the invention.

FIG. 2 is a partial sectional view taken along line 2-2 of FIG. 1 andshowing the upper bridge ring structure of the cell.

FIG. 3 is a greatly enlarged sectional view taken along line 3-3 of FIG.2, the curvature of the upper bridge ring edges being exaggerated forillustrative purposes.

FIG, 5 is a greatly enlarged partial sectional view of a portion of thelower bridge ring structure as shown in FIG. 1, the curvature of thelower bridge ring edges being exaggerated for purposes of illustration.

Similar reference characters refer to similar parts throughout theseveral views of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, theload cell comprises a piston member 10 mounted for reciprocal axialmovement within a cylinder member 12. Cylinder member 12 comprises acylindrical casing ring 14 mounted to a base 16 by a series of capscrews 18. Each cap screw 18 passes through a counterbored hole 20 inbase 16 and into threaded engagement with casing ring 14. The uppersurface of base 16 provided with an annular indentation 22 which definesa part of the pressure chamber of the load cell. A central plateau 21 isalso provided on the upper surface of base 16. A diaphragm 24,preferably formed of flexible sheet metal such as stainless steel, ispositioned over the upper surface of base 16 leaving a small space 23between it and plateau 21. Diaphragm 24 thus overlies the cell pressurechamber which comprises indentation 22 and space 23. Diaphragm 24 is inturn covered except for the clamped outer edge thereof by a neoprenedisc 25 to minimize friction with piston member 10. The outer edge ofdiaphragm 24 is then clamped in position adjacent the outer periphery ofthe cell between the base portion 26 of casing ring 14 and the uppersurface of base 16 as shown in FIG. I.

A passageway 28 is provided in base 16 in communication at one end withpressure chamber 22. At the other end 28a the passageway opens up toform an externally accessible connection. Passageway 28 and connection28a serve two function in the cell. For one they provide a passage forfilling pressure chamber 22 with a suitable hydraulic fluid. Oncepressure chamber 22 is filled with fluid, connection 28a then serves asa means for connecting a suitable pressure-sensitive indicatinginstrument (not shown) to the cell. The indicating instrument thenprovides a readout means for indicating the magnitude of weight or forceapplied to the cell. A second passageway and connection similar to 28and 28a may be provided in base 16 to act as an air vent when the cellis being filled with fluid. When all air bubbles are purged from thecell the vent is normally plugged and does not function during celloperation.

A further passageway 29 is provided into the cell through the side ofthe casing ting l4. Passageway 29 functions as a gauging hole to permitgauging of the cell by means of a feeler gauge inserted in the space 29abetween flanges 30 and 32. Space 620 decreases as the cell fills withfluid and thereby permits determination of the fill of hydraulic fluidwithin the cell.

Piston is generally cylindrical member having a circumferential flange30 adjacent the bottom end thereof. It will be seen by reference to FIG.1 that piston 10 is most readily mounted in casing ring 14 by invertingthe casing ting and inserting the piston from the underside thereofuntil flange 40 rests against a corresponding casing ring flange 32.

the top end of piston 10 is maintained in a central piston in casingting I4 and is braced against side thrusts by an upper annular bridgering 34. Upper bridge ring 34 is preferably formed from a hardened steeland is provided with a series of slots 36 about its periphery as shownin FIG. 2. Slots 36 cut deeply into the bridge ring from the centerdiameter edge 34a thereof. Thus, the bridge ring 34 of formed as aplurality of individual segments which are connected by a relativelynarrow band of metal adjacent to inner diameter edge 34b. Such aconstruction permits bridge ring 34 to readily flex during operation ofthe cell as will be understood from the following discussion,

Referring back to FIG. 1, bridge ring 34 is supported adjacent the topof the load cell by shoulder support means which are preferably integralwith casing ting 14 and piston member 10. The shoulder support meanspreferably comprise an integral shoulder 38 projecting from the innerwall of casing ring 14 and facing the bottom of the load cell in itsnormal operating position (FOG. 3). Shoulder 38 serves as an initialsupport for the upper bridge ring when the cell is assembled. Bridgering 34 is insert edgewise into the top of casing ring 14 before it isinverted for further assembly, and then rotated to horizontal and heldagainst shoulder 38 while the casing ring is inverted. To permit thisslots 39 (FIG. 3) are provided in opposite sides of shoulder 38 toaccommodate the edgewise insertion of bridge ring 34. when the diameterof flange 32 is large enough, bridge ring 34 may alternatively bedropped into position onto shoulder 39 when casing ring 14 is invertedfor assembly.

Piston member 10 is likewise provided with an integral shoulder 40 onthe outer surface thereof adjacent the top end. Shoulder 40, as shown inFIGS. 1 and 3, faces the top of the load cell in its normal operatingposition. As can be seen however, during assembly shoulder 40 will restface down against bridge ring 34. However, when the load cell in in itsnormal operating portions as shown in FIGS. 1 and 3, shoulder 40underlies the inner diameter edges 34bof upper bridge ring 34 and holdsit up in position in the load cell structure. It should be noted thatthe supported edge of bridge ring 34 is the relatively rigid integraledge 34b. This is done to provide added strength. At the same time,shoulder 38 on casing ring 14 overlies the outer diameter edge 34b ofbridge ring 34 and serves to prevent the bridge ring from beingaccidentally ejected from the top of the cell during operation.

As piston member 10 reciprocates axially within cylinder member 12, thereciprocating movement typically being on the order of a few thousandthsof an inch, upper bridge ring 34 deflects slightly to accommodate suchmovement. During such deflection, the edges of the bridge ring are urgedto pivot and/or slide on the adjacent piston and cylinder surfaces. Thebridge ring has the same tendency to pivot or slide under the influenceof heavy slide loading. It can be seen by reference to FIG. 3 that ifthe inner and outer diameter edges 34!) and 34aof the bridge ring areflat, pivoting is restricted and the sharp corners thereof may dig intoand bind on the adjacent piston and cylinder surfaces. Such binding mayseriously impair the accuracy and reproducibility of the cell.Accordingly, as shown in FIG. 3, upper bridge ring 34 is preferablyprovided with arcuate surfaces on the outer and inner diameter edges 34aand 34b. The arcuate edges are preferably formed with a radius equal toone-half the width of the bridge ring W" (FIG. 2). this insures that anymovement of the bridge ring edges will be essentially pure rollingmotion of the eliminating any vertical component. Thus, when the bridgering 34 deflects in response to movement of piston member 10, thearcuate edges freely pivot in a rolling manner. This greatly reducesfriction and eliminates the possibility of binding as would be the casewith the sharp-edged bridge ring. The particular combination ofdeflection and pivoting which occurs in the upper bridge ring of theinvention is hereinafter termed, in the specification and claims,pivotal deflection.

The bottom end piston 10 is also preferably supported by an annularbridge ring similar to upper bridge ring 34. This lower bridge ringfurther serves to support diaphragm 24 and neoprene disc 25 against theupward pressure of the hydraulic fluid. As shown in FIG. 1, lower bridgering 42 rests on disc 25 over diaphragm 24 and extends up into a bridgering aperture 44. Aperture 44 is defined under both flange 30 on pistonmember 10 and base portion 26 of casing ring 14 (FIG. 4). Preferably,lower bridge ring 42 is supported against the upward force due topressure in chamber 22 by a pair of annular wires 46 and 48. Wires 46and 48 are each positioned above lower bridge ring 42 and bearrespectively against shoulders 50 and 52 formed in piston member 10 andcasing ring 14. Wires 46 and 48, in effect, form substantiallyfrictionless pivots for the deflection of bridge ring 42 during movementof piston member 10, and they help maintain the acting area of the cellconstant. Lower bridge ring 42 is also preferably provided with arcuateouter and inner diameter edges 42a and 42b, the radii thereof alsopreferably being equal to one-half the width of the bridge ring. Theseedges permit lower bridge ring 42 to undergo pivotal deflection insubstantially the same manner and for the same advantageous reasons aspreviously discussed for upper bridge ring 34.

Loads are applied to the load cell through a loading head 54 which ismounted at the top of the load cell as shown in FIG. 1. Preferably,loading head 54 is supported on a rolling ball 56 as shown. The loadinghead thus supported may either tilt or move from side to side toaccommodate offcenter loading or cross loads. Ball 56 rests on ahardened steel load block 58 which is freely supported on the bottom ofa centrally located recess 60 in piston member 10. Load block 58 andball 56 are contained in a substantially centered position within recess60 by surrounding resilient cylinder 62 which may be formed of neopreneor the like. Loading head 54 also carried a second load block 64 whichis freely supported on the lower surface thereof. Load block 64 ispreferably partially inserted into an aperture 65 which is formed inloading head 54 to keep the load block centered. As used herein in thespecification and claims, the term freely supported as applied to theload blocks means that they are held in position without the use of capscrews or the like.

As shown in FIG. 1, resilient cylinder 52 extends over only a portion ofthe depth of recess 60 and partially encompasses ball 56. The use of acylinder of this type permits maximum side to side movement of loadinghead 54. In those applications, however, where the side-to-side movementof loading head 54 is preferably inhibited, the height of resilientcylinder 62 may be extended as shown by the dotted lined in FIG. I toencompass at least a portion of the upper block 64.

The workings of the load cell may be seriously impaired by the intrusionof friction producing or corrosive contaminants Accordingly, a flexibleprotective boot 66 is secured over the top of the load cell by clamps 68and 70 which are respectively secured about loading head 54 and casingring 14. For added protection against contamination, however, asupplementary shield 72, comprising an annular elastomeric sheet, ispreferably adhesively secured over upper bridge ring 34 to the topsurfaces of casing ting l4 and piston member 10. Supplementary shield 72thus serves to protect the moving parts of the load cell formcontamination in the vent that protective boot 66 fails.

it will be thus seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense. 7

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention, which as amatter of language, might be said to fall therebetween,

Having described my invention, what I claim as new and desire to secureby letters Patent is:

l. A hydraulic load cell of simplified construction comprising, incombination:

A. a cylinder member having a pressure chamber in its base,

8. a diaphragm extending across said chamber,

C. a piston member reciprocally mounted in said cylinder,

D. means providing lateral support for said piston member adjacent saiddiaphragm, and V E. an annular upper bridge ring disposed for pivotaldeflection between said cylinder and said piston members, said upperbridge and ring supported at a position spaced from said diaphragm byshoulder support means comprising a first shoulder around said pistonmember facing the top of said cell and underlying the inner diameteredge of said upper bridge ring, the upper surface of said upper bridgering adjacent said inner diameter edge being unsupported, and a secondshoulder around said cylinder surface facing the bottom of said cell andoverlying the outer diameter edge of said upper bridge ring, the undersurface of said upper bridge ring adjacent said outer diameter edgebeing unsupported.

2. A hydraulic load cell simplified construction comprising,

in combination:

A. a cylinder member having a pressure chamber in its base,

B. a diaphragm extending across said chamber,

C. a piston member reciprocally mounted in said cylinder,

D. an annular lower bridge ring resting over said diaphragm and disposebetween said cylinder member and said piston member and,

E. an annular upper bridge ring having arcuate inner and outer diameteredges being disposed for pivotal deflection between said cylinder andpiston members,

a. said upper bridge ring being supported by first shoulder around saidpiston member facing the top of said cell and underlying the innerdiameter edge of said upper bridge ring, the upper surface of said upperbridge ring adjacent said inner diameter edge being unsupported, and bya second shoulder around said cylinder facing the bottom of said celland overlying the outer diameter edge of said upper bridge ring, theunder surface of said upper bridge ring adjacent said outer diameteredge being unsupported.

3. A hydraulic load cell ad defined in claim 2 wherein said first andsecond shoulders are respectively integral with said piston and cylindermembers.

4. A hydraulic load cell as defined in claim 2 wherein said arcuateinner and outer diameter edges have a radius equal to one-half the widthof said upper bridgering.

5. In a hydraulic load cel comprising a cylinder member having apressure chamber in its base, a diaphragm extending across said chamber,a piston member reciprocally mounted in said cylinder, and an annularlower bridge ring resting over said diaphragm and disposed between saidcylinder member and said portion member, theimprovement comprising anannular upper bridge ring disposed for pivotal deflection between saidcylinder and said piston members and being sup ported therein withoutclamping by shoulder means comprising a first shoulder around saidpiston member facing the top of said cell and underlying the innerdiameter edge of said upper bridge ring, the upper surface of said upperbridge ring adjacent said inner diameter edge being unsupported, andsecond shoulder around said cylinder facing the bottom of said cell andoverlying the outer diameter edge of said upper bridge ring, the undersurface of said upper bridge ring adjacent said outer diameter edgebeing unsupported.

6. In a hydraulic load cell as defined in claim 5 having a protectiveflexible boot secured over said piston cylinder members to preventintrusion of contaminants, the further improvement comprising asupplementary shield comprising an annular elastomeric sheet adhesivelysecured to the top surfaces of said piston andcylinder members over saidupper bridge ring and serving to prevent the intrusion of contaminantsshould said boot fail.

7. A hydraulic load cell as defined in claim 5 including a passage meansthrough said cylinder member and communicating with said pressurechamber, said passage means functioning both as a means for filling saidpressure chamber with hydraulic fluid as a connection for an externalpressure-sensitive indicating instrument.

8. A hydraulic load cell as defined in claim 5 wherein said first andsecond shoulders are respectively integral with said piston and cylindermembers.

9. A hydraulic load cell as defined in claim 5 wherein said upper bridgering has arcuate surfaces on the inner and outer diameter edges thereofto facilitate pivotal deflection and prevent binding.

10. A hydraulic load cell as defined in claim 9 wherein the radius ofeach of said arcuate surfaces is equal to one half the width of saidupper bridge ring.

11. A hydraulic load cell as defined in claim 9 and further includingarcuate surfaces on the inner and outer diameter edges of said lowerbridge ring, said arcuate surfaces each having a radius equal toone-half the width of said lower bridge ring to facilitate pivotaldeflection and prevent binding.

12. A hydraulic load cell as defined in claim 5 including a recess insaid piston member, a resilient cylinder supported on the bottom of saidrecess and in substantially contiguous contact with the sidewallthereof, a first load block freely supported on the bottom of saidrecesses within said resilient cylinder, a loading head located abovesaid piston, a second load block freely supported on the lower surfaceof said loading head over said first load block, and rolling balldisposed in said recess within said resilient cylinder in position tocontact both said first and second load blocks during cell operation.

13. A hydraulic load cell as defined in claim 12 wherein the height ofsaid resilient cylinder is substantially less than the depth of saidrecess to permit side-to-side motion of said loading head.

14. A hydraulic load cell as defined in claim 12 wherein said the heightof said resilient cylinder is substantially equal to the depth of saidrecess and contiguously surrounds at least a portion of said second loadblock to inhibit side-to-side motion of said loading head.

Patent No. 3,633,695 Dat January ll, 1972 lnventol-(s) Chester D.Bradley It is certified that error appears in the above-identifiedpatentand that said Letters Patent are hereby corrected as shown below:

Column 2, line 23, after "ring" insert structure--; line 47, "5" shouldbe 4; line 62, after "16" insert is--.

Column 3, line 20, "62a" should be 29a--; line 22, after "is" insert a;line 25, "ting" should be ring-;

line 26, "40" should be 30; line 29, "ting" should be -ring-; line 31,delete "a" first occurrence; line 33, "center" should be outer; line 34,delete "the"; "of" should be -is--; line 42, "ting" should be -ring;line 46, "(FOG.3)." should be (FIG.3)-; line 48, "insert" should beinserted--;; line 55, "39" shouldbe 38; line 62,

"in" first occurrence should be is; line 63, "portions" should beposition. Column 4, line 6, "slide should be side--; line 17,"essentially" should be -substantially--; line 18, "the" should be-upper; line 58, after "by" insert a; line 59, "carried" should becarries; line 67, "52" should be 62. Column 5, line 9, "ting" should bering-; line ll, "form" should be -from; line 13, "be thus" should bethus be-; line 36, delete "and", and after "ring" insert being; lines41, 42, delete "sur-face"; line 46, after "cell" insert of; line 55,"being" should be and-. Column 6, 2 line 3, after "edges" insert each-;line 10, "portion" should be piston-; line 17, after "and" insert a;line 23, after "piston" insert and; line 30, delete "a"; line 34, after"fluid" insert and-; line 54, "sidewall" should be sidewalls; line 58,after "and" insert a; line 65, delete "said".

Signed and sealed this 27th day of June 1972.

(SEAL) Attest:

EDWARD Mal "LEI'GHELR,.JR0 ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents DRM PO-IOSO (10-69) USCOMM-DC 6O376-P69 U.S.GOVERNMENT PRINTING OFFICE: I959 0-366-334 Patent No. 3,633,695 ateJanuarv 11, 1972 lnventol-(s) Chester D. Bradley It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, line 23, after "ring" insert structure-; line 47, "5" shouldbe 4; line 62, after "16" insert -is..

Column 3, line 20, "62a" should be 29a; line 22, after "is" insert a;line 25, "ting" should be ring--;

line 26 "40" should be 30-; line 29 "ting" should be I --ring; line 31,delete "a" first occurrence; line 33, "center" should be -outer; line34, delete "the"; "of" should be is-; line 42, "ting" should .be -ring;line 46 (FOG. 3) should be (FIG. 3) line 48 "insert" should be inserted;line 55, "39" shouldbe 38-; line 62,

"in" first occurrence should be is; line 63, "portions" should beposition. Column 4, line 6, "slide'Tshould be side-; line 17,"essentially" should be substantially; line 18, "the" should be -upper-;line 58, after "by" insert a; line 59, "carried" should be carries; line67, "52" should be -62. Column 5, line 9, "ting" should be ring-; linell, "form" should be from; line 13, "be thus" should be thus be-, line36, delete "and", and after "ring" insert --being; lines 41, 42, delete"sur-face"; line 46, after "cell" insert --of; line 55, "being" shouldbe and-. Column 6 line 3, after "edges" insert each; line 10, "portion"should be piston; line 17, after "and" insert a; line 23, after "piston"insert and; line 30, delete "a"; line 34, after "fluid" insert and-;line 54, "sidewall" should be sidewalls; line 58, after "and' insert a;line 65, delete "said" Signed and sealed this 27th day of June 1972,

Attest:

EDv-IARD M01 LETCFIEIR JR0 ROBERT GOTI'SCHALK Antes-ting OfficerCommissioner of Patents FORM PO-105O (10-69) USCOMM-DC 60376-P69 9 U.S,GOVERNMENT PRINTING OFFICE 1959 0-366-334

1. A hydraulic load cell of simplified construction comprising, incombination: A. a cylinder member having a pressure chamber in its base,B. a diaphragm extending across said chamber, C. a piston memberreciprocally mounted in said cylinder, D. means providing lateralsupport for said piston member adjacent said diaphragm, and E. anAnnular upper bridge ring disposed for pivotal deflection between saidcylinder and said piston members, said upper bridge and ring supportedat a position spaced from said diaphragm by shoulder support meanscomprising a first shoulder around said piston member facing the top ofsaid cell and underlying the inner diameter edge of said upper bridgering, the upper surface of said upper bridge ring adjacent said innerdiameter edge being unsupported, and a second shoulder around saidcylinder surface facing the bottom of said cell and overlying the outerdiameter edge of said upper bridge ring, the under surface of said upperbridge ring adjacent said outer diameter edge being unsupported.
 2. Ahydraulic load cell simplified construction comprising, in combination:A. a cylinder member having a pressure chamber in its base, B. adiaphragm extending across said chamber, C. a piston member reciprocallymounted in said cylinder, D. an annular lower bridge ring resting oversaid diaphragm and dispose between said cylinder member and said pistonmember and, E. an annular upper bridge ring having arcuate inner andouter diameter edges being disposed for pivotal deflection between saidcylinder and piston members, a. said upper bridge ring being supportedby first shoulder around said piston member facing the top of said celland underlying the inner diameter edge of said upper bridge ring, theupper surface of said upper bridge ring adjacent said inner diameteredge being unsupported, and by a second shoulder around said cylinderfacing the bottom of said cell and overlying the outer diameter edge ofsaid upper bridge ring, the under surface of said upper bridge ringadjacent said outer diameter edge being unsupported.
 3. A hydraulic loadcell ad defined in claim 2 wherein said first and second shoulders arerespectively integral with said piston and cylinder members.
 4. Ahydraulic load cell as defined in claim 2 wherein said arcuate inner andouter diameter edges have a radius equal to one-half the width of saidupper bridge ring.
 5. In a hydraulic load cell comprising a cylindermember having a pressure chamber in its base, a diaphragm extendingacross said chamber, a piston member reciprocally mounted in saidcylinder, and an annular lower bridge ring resting over said diaphragmand disposed between said cylinder member and said portion member, theimprovement comprising an annular upper bridge ring disposed for pivotaldeflection between said cylinder and said piston members and beingsupported therein without clamping by shoulder means comprising a firstshoulder around said piston member facing the top of said cell andunderlying the inner diameter edge of said upper bridge ring, the uppersurface of said upper bridge ring adjacent said inner diameter edgebeing unsupported, and second shoulder around said cylinder facing thebottom of said cell and overlying the outer diameter edge of said upperbridge ring, the under surface of said upper bridge ring adjacent saidouter diameter edge being unsupported.
 6. In a hydraulic load cell asdefined in claim 5 having a protective flexible boot secured over saidpiston cylinder members to prevent intrusion of contaminants, thefurther improvement comprising a supplementary shield comprising anannular elastomeric sheet adhesively secured to the top surfaces of saidpiston and cylinder members over said upper bridge ring and serving toprevent the intrusion of contaminants should said boot fail.
 7. Ahydraulic load cell as defined in claim 5 including a passage meansthrough said cylinder member and communicating with said pressurechamber, said passage means functioning both as a means for filling saidpressure chamber with hydraulic fluid as a connection for an externalpressure-sensitive indicating instrument.
 8. A hydraulic load cell asdefined in claim 5 wherein said first and second shoulders arerespectively integral with said piston and cylinder members.
 9. Ahydraulic load cell as defined in claim 5 wherein said upper bridge ringhas arcuate surfaces on the inner and outer diameter edges thereof tofacilitate pivotal deflection and prevent binding.
 10. A hydraulic loadcell as defined in claim 9 wherein the radius of each of said arcuatesurfaces is equal to one half the width of said upper bridge ring.
 11. Ahydraulic load cell as defined in claim 9 and further including arcuatesurfaces on the inner and outer diameter edges of said lower bridgering, said arcuate surfaces each having a radius equal to one-half thewidth of said lower bridge ring to facilitate pivotal deflection andprevent binding.
 12. A hydraulic load cell as defined in claim 5including a recess in said piston member, a resilient cylinder supportedon the bottom of said recess and in substantially contiguous contactwith the sidewall thereof, a first load block freely supported on thebottom of said recesses within said resilient cylinder, a loading headlocated above said piston, a second load block freely supported on thelower surface of said loading head over said first load block, androlling ball disposed in said recess within said resilient cylinder inposition to contact both said first and second load blocks during celloperation.
 13. A hydraulic load cell as defined in claim 12 wherein theheight of said resilient cylinder is substantially less than the depthof said recess to permit side-to-side motion of said loading head.
 14. Ahydraulic load cell as defined in claim 12 wherein said the height ofsaid resilient cylinder is substantially equal to the depth of saidrecess and contiguously surrounds at least a portion of said second loadblock to inhibit side-to-side motion of said loading head.